PROJECT SUMMARY While clinical care for HIV has made tremendous advances, the majority of persons living with HIV in the US do not receive the evidence-based care that will allow them to fully extend life and improve health. Lack of effective HIV care is particularly problematic in the Southern region, the epicenter of the US HIV epidemic and where poverty, uninsurance, rurality, and a constrained health workforce further threaten effective care. Research suggests that system-level factors, or the structural and policy-related aspects of health care delivery, have the potential to improve quality of care and health outcomes. But little is known about their role in the context of HIV care delivery, quality of care, and health outcomes. The proposed research will study how two modifiable system-level factors?geographic accessibility to care and physician payment policies?affect quality of HIV care and population outcomes, including new HIV infections, along the HIV care continuum in the US South. Because racial and ethnic minorities face increased barriers to HIV care, we pay special attention to how these system-level factors may contribute to disparities in quality of HIV care and population outcomes along the HIV care continuum. The research involves developing a novel database that combines multiple data sources, including Medicaid administrative claims files, HIV surveillance data, and county and state characteristics from national datasets. Our approach will rely on state-of-the-art spatial network analysis and data visualization (mapping), statistical tests using econometric methods, and systems science forecasting techniques that have been used to study quality of care and population health outcomes. The work moves beyond examination of core quality of HIV care measures to include HIV-related preventive care measures that collectively are critical to reducing HIV morbidity and mortality. In investigating these factors, the study will answer a number of important questions. How do geographic accessibility, measured in travel time to receive care, and physician payment for services affect quality of HIV care in the South? Are these effects different among racial and ethnic minorities? Do improvements in geographic accessibility or increased physician payments reduce new HIV infections and racial and ethnic disparities along the HIV care continuum? The proposed study will address these questions and others. By quantifying the role of system-level factors in quality of HIV care and population health along the HIV care continuum, as well as understanding disparities in these effects, the research will provide valuable information to state and federal policy makers who seek to address systemic challenges to effective HIV care, efficiently allocate scarce resources, and improve public health.